usb: gadget: uvc: Fix use-after-free for inflight usb_requests

Currently, the uvc gadget driver allocates all uvc_requests as one array
and deallocates them all when the video stream stops. This includes
de-allocating all the usb_requests associated with those uvc_requests.
This can lead to use-after-free issues if any of those de-allocated
usb_requests were still owned by the usb controller.

This is patch 2 of 2 in fixing the use-after-free issue. It adds a new
flag to uvc_video to track when frames and requests should be flowing.
When disabling the video stream, the flag is tripped and, instead
of de-allocating all uvc_requests and usb_requests, the gadget
driver only de-allocates those usb_requests that are currently
owned by it (as present in req_free). Other usb_requests are left
untouched until their completion handler is called which takes care
of freeing the usb_request and its corresponding uvc_request.

Now that uvc_video does not depends on uvc->state, this patch removes
unnecessary upates to uvc->state that were made to accommodate uvc_video
logic. This should ensure that uvc gadget driver never accidentally
de-allocates a usb_request that it doesn't own.

Link: https://lore.kernel.org/7cd81649-2795-45b6-8c10-b7df1055020d@google.com
Reviewed-by: Daniel Scally <dan.scally@ideasonboard.com>
Reviewed-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Suggested-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Tested-by: Michael Grzeschik <m.grzeschik@pengutronix.de>
Signed-off-by: Avichal Rakesh <arakesh@google.com>
Link: https://lore.kernel.org/r/20231109004104.3467968-4-arakesh@google.com
Signed-off-by: Greg Kroah-Hartman <gregkh@linuxfoundation.org>

1 files changed, 1 insertions, 9 deletions

diff --git a/drivers/usb/gadget/function/uvc_v4l2.c b/drivers/usb/gadget/function/uvc_v4l2.c
index 904dd283cbf7..c7e5fa4f29e0 100644
--- a/drivers/usb/gadget/function/uvc_v4l2.c
+++ b/drivers/usb/gadget/function/uvc_v4l2.c
@@ -468,11 +468,11 @@ uvc_v4l2_streamoff(struct file *file, void *fh, enum v4l2_buf_type type)
 	if (type != video->queue.queue.type)
 		return -EINVAL;
 
-	uvc->state = UVC_STATE_CONNECTED;
 	ret = uvcg_video_disable(video);
 	if (ret < 0)
 		return ret;
 
+	uvc->state = UVC_STATE_CONNECTED;
 	uvc_function_setup_continue(uvc, 1);
 	return 0;
 }
@@ -507,14 +507,6 @@ uvc_v4l2_subscribe_event(struct v4l2_fh *fh,
 static void uvc_v4l2_disable(struct uvc_device *uvc)
 {
 	uvc_function_disconnect(uvc);
-	/*
-	 * Drop uvc->state to CONNECTED if it was streaming before.
-	 * This ensures that the usb_requests are no longer queued
-	 * to the controller.
-	 */
-	if (uvc->state == UVC_STATE_STREAMING)
-		uvc->state = UVC_STATE_CONNECTED;
-
 	uvcg_video_disable(&uvc->video);
 	uvcg_free_buffers(&uvc->video.queue);
 	uvc->func_connected = false;